A passive optical network (PON) is one system for providing network access over “the last mile.” The PON is a point-to-multi-point (P2MP) network comprised of an optical line terminal (OLT) at the central office, an optical distribution network (ODN), and a plurality of optical network units (ONUs) at the customer premises. Ethernet passive optical network (EPON) is a PON standard developed by the Institute of Electrical and Electronics Engineers (IEEE) and specified in IEEE 802.3ah, which is incorporated herein by reference as if reproduced in its entirety. In EPON, a single fiber can be used for both the upstream and the downstream transmission with different wavelengths. The OLT implements an EPON Media Access Control (MAC) layer for transmission of Ethernet Frames. The Multi-Point Control Protocol (MPCP) performs the bandwidth assignment, bandwidth polling, auto-discovery, and ranging. Ethernet frames are broadcast downstream based on the Logical Link Identifier (LLID) embedded in the preamble of the Ethernet frame. Upstream bandwidth is assigned based on the exchange of Gate and Report messages between an OLT and an ONU.
Ethernet over Coax (EoC) is a generic name used to describe all technologies which can be used for transmission of Ethernet frames over a unified optical-coaxial (coax) network. The name comes from the fact that, except for Data Over Cable Service Interface Specification (DOCSIS), all these technologies have in common that the Ethernet Frames are transmitted in the MAC layer. Different EoC technologies exist, including Multimedia over Coax Alliance (MoCA), G.hn (a common name for a home network technology family of standards developed under the International Telecommunication Union (ITU) and promoted by the HomeGrid Forum), HomePNA Alliance (HPNA), and Home Plug Audio/Visual (A/V), and they have been adapted to run the outdoor coax access from an ONU to an EoC Head End with connected Customer Premises Equipment (CPEs) located in the subscriber homes.
There is a rising demand which requires the use of EPON as an access system to interconnect with multiple coax cables to terminate the Coax Network Units (CNUs) located in the subscriber's home with an Ethernet PON over Coax (EPoC) architecture. However, none of the above-referenced EoC technologies provides a unique way to identify the EoC Head End that connects the EPON and Coax networks. In addition, none of the above-referenced EoC technologies provide a mechanism measuring the round trip delay time in a unified optical-coaxial network. Consequently, there is a need in the art for methods and apparatus to determine the round trip delay time (RTT) including the round trip delays over both the optical and coaxial segments of a unified optical-coaxial network.